Electrical change-over



May 30, 1939. APPA 2,160,005

ELECTRICAL CHANGE -OVER Filed Sept. 10, 1935 FEE E- I 3 1g E INVENTOR. CH STER TA PPA u A TTORNE Y.

Patented May 30, 1939 PATENT OFFICE ELECTRICAL CHANGE-OVER Chester Tappan, New York, N. Y., assignor to General Talking Pictures Corporation, New York, N. Y., a corporation of Delaware Application September 10, 1935, Serial No. 39,924

2 Claims.

The present invention relates to improvements in electrical change-overs, that is, a simple and easily operated control change-over system for use in conjunction with soundonfilm theatrical projection apparatus, one object of the invention being the provision of means to control through a push-button, instead of the regular wheel op-. erated fader, and which is more eflicient in use and in operation'and preventing any interruption in the transmission of sound when a change-over is made from one projector to the other.

Another object of this invention is the provision of means to produce an automatic dowsing of the light on one projector simultaneously with the opening of the aperture on. the other projector. I 7

Still another object of the invention is the provision of an apparatus to control the volume from either of two projecting machines or upon a non-synchronized apparatus or disc electrical pick-up, and to also change over the exciting lamp circuit from one sound head to the other or vice versa. I 7

Still another object of this invention is the provision of means whereby the exciter lamp in the sound head which is not in service can be energized while the other machine is running, permitting the necessary focussing in the first machine so that the optical system can be tested and adjusted.

With the foregoing and other objects in view, which will appear as the description proceeds, the invention resides in the combination and arrangement of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed can be made within the scope of what is claimed without departing from the spirit of the invention.

In the accompanying drawing:-

Fig. 1 is a diagrammatic View of one electrical arrangement of the present change-over system. Fig. 2 is a similar view of a modified circuit.

Fig. 3 is a diagram of an additional wiring that can be used with either one of the previous diagrams.

Referring to the drawing, and more particularly to Fig. 1 thereof, the numerals I and 2 designate the input from the left hand photoelectric cell amplifier and terminals 3 and 4 the right hand photoelectric amplifier output. A disc pickup P is to be connected to the terminals 5 and 6 and is what is known in common parlance as a non-synchronized pick-up, so that musical and other records may be played over the amplifying system as and when desired. A supply rectifier R is provided with the output terminals 1 and 8 while the terminals 9 and I0 indicate the conductors leading to the exciting lamps EE' for the two sound heads (not shown). Beginning with the terminals I2, it will'be noted that the terminal 2 has a conductor 2 connected to the output at terminal ll while terminal I is connected through a conductor l' to a pair of contacts of a switch l3 which is also utilized to transfer the input from the sound film to the sound disc terminal 5 and vice versa. From this point the switch I3 is connected to a pole of the double-pole-double-throw locking relay switch l4.

When switch I4 is in the up position the sound is led through to the input of the Ttype attenuator l5 at which point the volume is controlled and thence to the other output terminal to complete the circuit. Similarly the terminal 3- 0f the right hand machine has the sound led through conductor 20 to a terminal 2| on the switch l4, and with the switch in the down position the sound in turn is led through conductor 22 to the attenuator I5, and hence through conductor 24 to the output terminal l2.

Similarly the positive -volt input is led through conductor 24 to the other side of the switch I4 and two terminals 9 and Hi, this depending upon the position of the switch, whether it is up or down. Hence the lines l9 and IS a and the sound from each respective machine are operated simultaneously and each in turn is operated with its own respective machine.

The switch 14 constitutes a double coil relay or a two-position relay and the contacts are so arranged that they make before they break. This is desirable so as not to open either the sound or the exciting lamp circuit, and also as there is no unloading of either the amplifier or rectifier respectively. The coils in this relay are wound respectively for 10 volts direct current, and the push button it when operated will cause the switch I4 to move to its up-position and remain there after the push button is released, as this is a locking type relay. Therefore, if the push button I! is operated the switch will move to its down position and in a like manner will remain locked, causing the transfer of the sound and the exciting lamp from one machine to the other.

It will be noted that a switch I8 is so connected that at such times as the left hand machine for instance is in operation, the right hand machine will have'its exciting lamp energized for focussing purposes or vice versa. This switch is also provided with a neutral position so that it is completely out of circuit during normal operation of the machine. Thus it will be seen that a means is provided for emergencies due to possible failure of the relay or the parts of the circuit, and also for testing the respective eXciter lamps and optical systems of one machine while the other machine is in projecting operation.

Although the attenuator I5 is here shown as connected in the circuit normally in the box within the projecting booth, it is to be noted that the same may be placed at any point wherever the conducting line or circuit may be placed, to be operated at a remote point or in the auditorium, so that a better quality of sound suitable to the capacity or every part of the auditorium may be obtained, or for that matter a duplicate attenuator placed in series with this attenuator l5 for remote adjustment may be employed.

It will be further noted that the pilot lamps I9 and i9 are placed in circuit for the convenience of the operator in order that at a glance at the front wall of the booth an immediate indication as to which machine is in operation, is given.

As it is preferred to use heater type tubes in the amplifiers used in conjunction with this change-over system, there is no difliculty with noise in the sound circuit when transferring from one exciter lamp to the other. If, however, this noise should occur, a small relay 2! is employed, the output of the amplifier being connected to the terminals 22' and 23' while the winding of this relay is connected across the actuating coil of the other relay. This auxiliary relay is a fast-acting relay so that it will actuate before relay l4, thus short-circuiting the output of the amplifier until such time as a complete transfer has been accomplished, the same becoming deenergized the instant the push-button is released,

and permitting the voice currents to flow through is known as in some instances to be higher or lower than the output of the other machine. Thus, by anticipating this, the individual attenuator is regulated so as to compensate for this 'level duringthe transfer with the result that a uniform output from the main amplifier is maintained.

From the foregoing description, taken in connection with the drawing, it is evident that although the present arrangement shows circuits an attenuator interposed in the circuit for controlling the quality of the sound originating in either apparatus, and a switch for each exciter lamp whereby either exciter lamp may be energized independently of the operation of its particular apparatus.

2. An electrical control mechanism, including in combination two sound reproducing apparatus each having an exciter lamp, twoelectrical networks, one interposed between each apparatus ing electrically actuated switch common to both networks, one of the electrical members of which is adapted to be energized by one of the respective push buttons, two pilot lights, one for each V and including each a push button, a double actapparatus, and one of which at a time is adapted to be energized when the switch is operated by its respective push button, and a T-type attenuator in said network for controlling the quality of sound originating in either apparatus and adapted to be connected in the networkwhen said double acting switch is in either closed position.

CHESTER TAPPAN. 

